Automatic document presence, skew and width detection method and apparatus for a document scanner

Abstract

A document scanner method and apparatus is provided which allows for the detection of the presence and size of a document to be scanned. The scanner is also able to determine whether the document being scanned is skewed. The document scanner includes an automatic document feeder (ADF), which includes a light pipe. The light pipe on the ADF redirects light from a light source to extra CCD pixels in a CCD array. Accordingly, when a document is present, the document will come between the light pipe and the light source and the extra CCD pixels in the CCD array will not detect light. When this occurs, a controller will determine that a document is present and will send commands to the ADF to feed the document forward and to the scanner to begin the scanning process. Similarly, other light pipes along the document scan path redirect light to extra CCD pixels of the CCD array and permit document size and document skew to be determined.

What is claimed is: 
     
       1. A document scanner including a document scan area and having an automatic document presence detection system, said automatic document presence detection system comprising: a light source having individual pixels extending across one side of said document scan area, said light source directing a strip of light toward said document scan area;   a light sense means having individual pixels extending across an area corresponding to said light source, said light sense means detecting light emitted from said light source, said light sense means extending outside the strip of light of said light source, such that said light sense means comprises extra pixels relative to said light source;   an automatic document feeder, said automatic document feeder extending across a second side of said document scan area opposing said light source, such that light from said light source directed toward said document scan area passes through said document scan area and toward said automatic document feeder when a document is not present;   a light pipe positioned in said automatic document feeder with a first end at a predetermined position adjacent said document scan area and a second end at a predetermined position outside of said strip of light of said document scan area, said light pipe being so positioned that light directed from said light source toward said document scan area impinges said first end of said light pipe, passes through said light pipe, exits said second end of said light pipe and is directed toward a predetermined number of said extra pixels in said light sense means when a document is not present in said document scan area, and when a document is present in said document scan area light does not pass through said document scan area to said light pipe and said extra pixels in said light sense means; and   a controller for turning on individual pixels of said light source that correspond to the position of said first end of said light pipe at predetermined intervals, said controller being responsive to said extra pixels of said light sense means, whereby if light is detected by said extra pixels of said light sense means the controller continues turning on said light source and monitoring said light sense means at predetermined intervals and if light is not detected by said extra pixels of said light sense means the controller instructs said automatic document feeder to begin feeding a document and the controller initiates the scanning process.   
     
     
       2. The document scanner according to claim 1, further comprising a second light pipe positioned in said automatic document feeder with a first end at a predetermined position adjacent said document scan area near an edge of said document scan area and a second end at a predetermined position outside of said strip of light of said document scan area, said second light pipe being so positioned that light directed from said light source toward said document scan area impinges said first end of said second light pipe, passes through said second light pipe, exits said second end of said second light pipe and is directed toward a second set of said extra pixels in said light sense means when a document is skewed in said document scan area, and when a document is not skewed in said document scan area light does not pass through said document scan area to said second light pipe and said second set of extra pixels in said light sense means, thus no light is detected by said second set of extra pixels when said document is not skewed. 
     
     
       3. The document scanner according to claim 2, further comprising a plurality of light pipes positioned in said automatic document feeder each with a first end at a predetermined position adjacent said document scan area and each with a second end at a predetermined position outside of said strip of light of said document scan area, said plurality of light pipes being so positioned that light directed from said light source toward said document scan area impinges one or more of said light pipes depending on the size of the document in the document scan area, the light passes through one or more of said light pipes, exits said second end of said one or more light pipes and is directed toward a third set of said extra pixels in said light sense means, the controller then selects a paper size depending on which of said plurality of light pipes light was able to impinge or not impinge. 
     
     
       4. A document scanner including a document scan area and having an automatic document presence detection system, said automatic document presence detection system comprising: a moving light source having individual pixels extending across one side of said document scan area, said light source directing a strip of light toward said document scan area;   a light sense means having individual pixels extending across an area corresponding to said light source, said light sense means detecting light emitted from said light source, said light sense means extending outside the strip of light of said light source, such that said light sense means comprises extra pixels relative to said light source;   a scanner lid, said scanner lid extending across a second side of said document scan area opposing said light source, such that light from said light source that is directed toward said document scan area passes through said document scan area and toward said scanner lid when said scanner lid is shut and a document is not present;   a means for determining whether said scanner lid is open or shut, such that said document presence system will only monitor for the presence of a document if said scanner lid is shut;   a light pipe positioned in said scanner lid with a first end at a predetermined position adjacent said document scan area and a second end at a predetermined position outside of said strip of light of said document scan area, said light pipe being so positioned that light directed from said light source toward said document scan area impinges said first end of said light pipe, passes through said light pipe, exits said second end of said light pipe and is directed toward a predetermined number of said extra pixels in said light sense means when a document is not present in said document scan area, and when a document is present in said document scan area light does not pass through said document scan area to said light pipe and said extra pixels in said light sense means; and   a controller for turning on individual pixels of said light source that correspond to the position of said first end of said light pipe at predetermined intervals, said controller being responsive to said extra pixels of said light sense means, whereby if light is detected by said extra pixels of said light sense means the controller continues turning on said light source and monitoring said light sense means at predetermined intervals and if light is not detected by said extra pixels of said light sense means the controller initiates the scanning process.   
     
     
       5. The document scanner according to claim 4, further comprising a multitude of light pipes positioned in said scanner lid each of said multitude of light pipes with a first end at a predetermined position adjacent said document scan area near an edge of said document scan area and a second end at a predetermined position outside of said strip of light of said document scan area, said multitude of light pipes being so positioned that light directed from said light source toward said document scan area impinges said first end of one or more of said multitude of light pipes, passes through said one or more of said multitude of light pipes, exits said second end of said one or more of said multitude of light pipes and is directed toward a second set of said extra pixels in said light sense means when a document is skewed in said document scan area, and when a document is not skewed in said document scan area light does not pass through said document scan area to any of said multitude of light pipes and said second set of extra pixels in said light sense means, thus no light is detected by said second set of extra pixels when said document is not skewed. 
     
     
       6. The document scanner according to claim 5, further comprising a plurality of light pipes positioned in said scanner lid each with a first end at a predetermined position adjacent said document scan area and each with a second end at a predetermined position outside of said strip of light of said document scan area, said plurality of light pipes being so positioned that light directed from said light source toward said document scan area impinges one or more of said plurality of light pipes depending on the size of the document in the document scan area, the light passes through one or more of said plurality of light pipes, exits said second end of said one or more of said plurality of light pipes and is directed toward a third set of said extra pixels in said light sense means, the controller then selects a paper size depending on which of said plurality of light pipes light was able to impinge or not impinge.